1. Field of the Invention
The present invention relates to an information recording method for writing over old digital information previously recorded on a recording medium, such as a phase-change optical disk for which the updating and the recording of data (hereinafter referred to as overwriting) can be performed, and also relates to an information recording apparatus for performing the above method.
2. Description of the Related Art
Generally, digital information that is to be recorded on a recording medium, such as an optical disk, is formed into information blocks, the volume of each of which corresponds to that of an error correction unit, such as an ECC (Error Correcting Code) block in an error correction process. ID information is added at the head of each information block to serve as address information on the recording medium. Therefore, when the above error correction unit is used to record new information over part of the information previously recorded on a rewritable recording medium, based on the ID information, a search is made for the first position occupied by the previously recorded digital information that is to be overwritten, and beginning at that first position, the overwriting of data is performed by the error correction unit.
Normally, a recording medium, such as an optical disk, is moved (rotated, when speaking of an optical disk) at a predetermined speed relative to an optical pickup for recording/reproducing digital information. The digital information is recorded at specific locations on the recording medium, based on a recording clock that is synchronized with the predetermined speed.
However, if the volume of the digital information to be recorded is M times (M is an integer of 1 or greater) that of the above-mentioned predetermined error correction block, due to the poor rotational control available with an optical disk, adequate positional accuracy can not be obtained when overwriting digital information. Thus, part of the data at the end of the information used to rewrite an information block may be so recorded that it overlaps and changes a portion of a succeeding block that should not be rewritten, i.e., the first portion of the succeeding information block wherein address information and ID information, such as a sync signal, are generally recorded. Since the ID information is used as control information when a recording/reproducing device exercises movement control, stable recording/reproducing control can not be performed if the ID information is destroyed by the rewriting operation.
Conventionally, therefore, when information is being rewritten, to prevent the overwriting and destruction of ID information, which should not be rewritten, at the head of the next information block, i.e., the information block that immediately follows the one that is to be rewritten, the aforementioned ID information and dummy data for which error correction can be performed are newly generated, and are added at the end of the new digital information that is to be recorded. Further, to standardize the updating/recording process, information obtained by excluding the ID information and the dummy data that is to be written at the head of the following information block is employed as the new digital information, and the updating and recording of information in the target information block is effected, beginning at a position following data previously recorded in the head portion of the block, ID information and other information that is written at a location originally occupied by dummy data.
That is, conventionally, the head portion of the information block that is to be rewritten is not changed, but ID information and newly generated dummy data are written in the head portion of the following information block, which should not be rewritten.
Since dummy data constitutes all the information in an information block for which the performance of error correction is permitted, the original data can be recovered by performing error correction. However, dummy data or old digital information, i.e., data differing from that which should be included, is present in the information block beginning at the position whereat new digital information and old digital information are coupled together (the first ECC block of new digital information and another ECC block, following the final ECC block of the new digital information, in which old digital information is recorded). Therefore, the capability of performing an error correction process for the information block at the coupled portion is deteriorated. That is, since the correction capability (e.g., the number of correctable words) for an information block as an error correction unit is determined in advance, if erroneous dummy data or old digital information is present at the beginning, errors that occur due to an original factor, such as a scratch on a disk, can not be corrected at the same time as time errors due to the dummy data and the old digital information are corrected.
To resolve the above shortcomings, it is an object of the present invention to provide an information recording method for reducing, during an overwriting process, the deterioration of the error correction capability for an information block at a coupled portion, and also to provide an information recording apparatus for performing the above method.
To achieve the above object, according to the present invention, there is provided an information recording method, whereby new digital information is employed to update a part of old digital information that has been recorded on an information recording medium and that has been separated by adding for each error correction unit control information that has been determined in advance, comprising: a latest update location detection step of employing the volume of the new digital information to detect the latest update position on the recording medium for the old digital information that is to be updated; an information reading step of reading a predetermined volume of old digital information that has been recorded following the latest update position detected; and a recording step of sequentially recording, following the recording of the new digital information, a part, which at least includes the control information, of the predetermined volume of the old digital information that has been read at the information reading step.
According to the present invention, at the latest update location detection step, before the updating and the recording of the new digital information are performed, the latest update location of the old digital information that is to be updated is detected. Then, at the information reading step, a predetermined volume of old digital information is read that was recorded at a succeeding position following the latest update location. In the updating and recording process, after the new digital information has been recorded, at least a portion of the old digital information that was read at the information reading step is recorded.
Therefore, instead of the conventional dummy data that is not related to the information that should have been recorded, the old digital information that should have originally been recorded is again recorded in the portion whereat the new, updated digital information and the old digital information are coupled together. Therefore, based on the old digital information that should have originally been recorded, it is possible to reduce the deterioration of the error correction capability for an ECC block that includes the above coupled portion for which error correction encoding has been performed.
Also, according to the present invention, there is provided an information recording apparatus, in which new digital information is employed to update a part of old digital information that has been recorded on an information recording medium and that has been separated by adding for each error correction unit control information that has been determined in advance, comprising: latest update location detection means for employing the volume of the new digital information to detect the latest update position on the recording medium for the old digital information that is to be updated; information reading means for reading a predetermined volume of old digital information that has been recorded following the latest update position detected; and recording means for sequentially recording, following the recording of the new digital information, a part, which at least includes the control information, of the predetermined volume of the old digital information that has been read by the information reading means.